The present invention relates to a device for dispersing a substance in a liquid.
Devices of this type serve to form a dispersion by finely distributing the substance in a liquid. The substance can be present as a solid, liquid or gaseous phase or also as a mixture of different phases. Wetting and homogeneously distributing the substance during the mixing process is often problematic. If the substance is a powder, there is also the risk of dust comprising unwetted powder undesirably forming in the environment.
It is known to supply liquid and substance to a dispersing chamber and to work them intensively by means of a dispersing tool in order to achieve fine distribution of the substance (see e.g. patent specifications EP-B1-436 462 and EP-B1-648 537 by the same applicant or patent specification EP-B1-587 714). However, it has been shown that wetting the substance with liquid is problematic and can result in undesired inhomogeneities in the dispersion. If, for example, a powdered substance is supplied, lumps can form in the mixing zone, i.e. the zone in which the substance comes into contact with the liquid, and these lumps clog the substance supply line or impede homogeneous distribution of the substance in the liquid. The known dispersing devices also have the disadvantage that the suction capacity is dependent upon the liquid throughput and the pressure at the outlet, with the result that the suction capacity may be too low to be able to suck in and wet a sufficient quantity of the substance to be dispersed.
Devices for producing a dispersion of gas and liquid are known from patent specifications U.S. Pat. No. 3,119,339 and U.S. Pat. No. 3,932,302. These devices comprise an eccentrically arranged gearwheel with internal teeth which mesh with a pinion, and a crescent-shaped insert. Devices of this type have inter alia the disadvantage that they are unsuitable for the dispersal of powdered substances. As the latter are virtually incompressible, the meshing of the internal teeth with the pinion would generate forces so great that the device would be damaged, e.g. the walls of the teeth or the pinion or possibly the bearings would be damaged. It is also disadvantageous that the throughput and therefore the dispersion volume producible per unit time are relatively low.
Devices which have radially displaceable vanes for producing a variable working volume are known from patent specifications U.S. Pat. No. 3,936,246 and U.S. Pat. No. 6,616,325 B1. This has the disadvantage that narrow gaps are formed, which can cause accumulation of the substance to be dispersed. Especially if the substance is a powder, this accumulation can lead to the vanes jamming in the guides and, ultimately, to failure of the device.
A device which has a cylinder rotating in a tube for the production of an emulsion is known from patent application US-A1-2002/0089074. The device has inter alia the disadvantage that it is poorly suited to the dispersal of powdered substances because pumping means of complex design have to be provided for the introduction of these substances.
Starting from this prior art, an object of the present invention is to propose a device which allows a substance to be sucked in and distributed in a liquid as homogeneously as possible in a simplified and improved manner.